ANIMALS, PARASITES and ENDANGERED SPECIES

Lesson 3 ANIMALS, PARASITES and ENDANGERED SPECIES Aim Discuss the existence of animals in the ecosystem. ANIMALS IN THE ECOSYSTEM Beetle Insecta Animals have carried out diversification so that they occupy many ecological niches. Herbivores form an essential link in the food chain. They are eaten by carnivores, which in turn are eaten by other carnivores. Many animals are parasites, or scavengers, or feed on sediments. Every animal has adaptations, such as sense organs and teeth enabling the animal to find and use food. Some use a wide variety of foods, while others specialise. Animals have features such as camouflage and protective shells to enable them to cope with predators. They are also in competition with each other for the scarce resources. This includes food and a place to live. The interactions between predator and prey have involved a co-evolution of these different parts of the ecosystem. That is, evolution of prey is affected by evolution of predators and vice versa. Parasites also play a role in an ecosystem. Parasites that are harmful, but do not usually kill their hosts, must be able to overcome defensive adaptations which both animals and plants have evolved to protect themselves. One example of this is behavioural defences, such as sheep avoiding open pastures in spring when roundworm eggs are due to hatch from the ground. Plants and animals can cooperate, in the sense that food is provided by the plants, and various animals effect pollination and seed distribution. A well-known example of this is the pollination of flowers by insects and bats which in turn receive nectar. Cooperative behaviours are also common within species. Ants and bees who live in colonies are a good example of individuals cooperating together to ensure their survival. There are a great variety of strategies used by animals to survive and reproduce. When there is an abundance of food in the ecosystem, the animals reproduce in quantity. However, when there is intense competition for food, the animals need to develop a more effective use of the available resources and they care for the young for a prolonged period. In those cases where the ecosystem is stable, as in the tropics, the competition leads to complex life cycles and intricate adaptations, both in structure and behaviour. Migration enables animals to move from place to place, enabling them to locate food, avoid predators, seek shelter, and to reproduce with more effectiveness.

Through migration, birds and other animals can feed and reproduce in areas where food is seasonally abundant. The migration of animals is only limited by the food supply, the terrain, and the capabilities of the individual animals for locomotion. Animals in the Human Community Since humans appeared on earth, they have lived in close proximity and association with other animals. Throughout much of the history of humans, they have lived as hunter-gatherers who depended on wild animals for food and clothing. Humans also found a source of aesthetic pleasure and spiritual strength in the animal life that existed around them. This is evidenced, by the remarkable paintings of animals in many parts of the world. These drawings are usually to be found in caves. The religious practices of many races show the veneration of humans for animals. For instance, the native North Americans venerated the bear, the wolf, and the eagle in an attempt to acquire the power, wisdom, courage and speed that these animals were said to possess. Similarly in Africa, the lion was seen as possessing great strength, the cheetah great speed and so on. Human societies continue to exhibit traces of animal relationships. The aesthetic appeal of animals is expressed in the mosaics of ancient Greece, Rome and Egypt, in the paintings of the masters of the renaissance, and in countless works of more recent artists. The ancient Egyptians had several gods that had animal heads, the principle ones being: Amun-ra the creator (who took on the persona of Kknum) and Hershefi, who were ram s-headed. Anubis was jackal-headed, Thoth, ibis-headed and Horus was hawk-headed. Many ancient Egyptian towns had animals for gods, for example, the baboon and the ibis of Hermopolis, lions in some of the Nile Delta towns, cats at Bubastis, bulls at Memphis and crocodiles in the Fayum. Mystical feelings towards animals are reflected in myths and folklore and in many animal stories for children. It is quite remarkable how many sports teams adopt an animal for the name of the club. For example: the ice hockey team the Montreal Bears, and the basketball team the Chicago Bulls. Despite highly developed technology and agriculture, and the domestication of many species, humans still depend on wild stocks of a variety of other animals for food and other products. However, unmanaged commercial exploitation has greatly reduced this resource and it has driven some species to the brink of extinction. As humans have advanced from hunting to agriculture, the relationships between animals and humans has changed. The animals that preyed on livestock or that destroyed crops were greatly reduced or eliminated and the alteration of the landscape destroyed the habitats of other species. As man concentrated in towns and cities, animals such as rats multiplied and became important carriers of disease. Humans have domesticated some animals for food, clothing, power, transport and companionship, but how this came about is a matter for speculation. By the process of protection, selected breeding, humans changed the early domesticated forms of animals into highly productive dairy and beef cattle, sheep, pigs and poultry. Also contributing to human welfare in the form of pets are dogs, cats, guinea pigs, and many more animals, while guide dogs are valuable to the blind and other dogs for rescue, tracking or security work. However, as humans continue to spread across planet earth they encroach on, or pollute the environments of many animals. Therefore the remaining habitats are becoming smaller and smaller. Unless this trend is reversed in the near future, much of the animal life on earth faces extinction. This poses dire consequences for future human existence.

ANIMALS An animal is defined as: Any member of the kingdom Animalia, which comprises all of the multicellular organisms that obtain energy by ingesting food and have cells organised into tissues. They differ from plants in that plants manufacture nutrients from inorganic substances by means of photosynthesis, and from fungi, which feed by absorbing organic matter in which they are normally embedded. Animals, in contrast, actively find their food and digest it internally. Associated with this mode of nutrition are many other features that distinguish animals from other life forms. Animals have special tissue systems that enable them to move freely in their search of food, or for those fixed in one place during most of their lives (sessile animals), to draw the food towards them. Animals have also developed a nervous system and complex sense organs that enable them to monitor the environment, and, in association with their movement, to respond flexibly and rapidly to changing stimuli. Most of the animal species, in contrast to plants, have a limited growth pattern and reach a characteristic well-defined shape and size by the time they reach maturity. Animals are predominantly sexual and birth is by means of an embryo. The conspicuous difference between plants and animals first led scientists to form a division of all life into two kingdoms: Plantae - The Plant Kingdom Animalia - The Animal Kingdom The plant kingdom is the subject of botanical science and the animal kingdom of zoology. Animals and plants are similar in fundamental structure while forming two divergent branches of one tree of life. Both transform nutrient into tissue, but while plants assimilate the nitrogen and carbon in the air and build up their tissues by absorbing salts from the soil, animals can only assimilate these chemical elements and compounds after the plants have formed them into organic compounds. Thus, plants are the great food producers and animals are the food consumers. Equilibrium is maintained by their joint actions. Animals are grouped according to anatomical structure. A porpoise looks like a fish, but is altogether different. It has the internal structure of a land animal, breathes with lungs, is warmblooded and suckles its young. Therefore it is grouped as a mammal and not a fish. The platypus lays eggs like a bird, yet their internal structure shows them to be a mammal. Conversely, animals of very different outward appearance may be almost identical in internal structure and they must be grouped together. The kingdoms are the first and highest division of living things. These divisions are further divided as follows: Kingdom to phyla (also known as sub kingdoms) Phyla to class Class to order Order to family Family to genera Genera to species For example, the domestic dog's species is determined as such: Kingdom - Animalia Phylum - Vertebrata (back-boned animals) Class - Mammalia (back-boned animals which suckle their young) Order - Carnivora (flesh eating mammals) Family - Canidae (dog-like)

Genus - Canis (dog) Species - familiaris (domestic dog) Domestic dogs can be further divided by breeds, but in most instances, this has been a selection process induced by humans. Generally speaking, a single species contains all the animals so far identical in form that they cannot be separated. They can interbreed freely and have fertile offspring. The information below shows the chief phylum and classes of the animal kingdom: 1. Vertebrates with Backbones PHYLUM AND CLASSES OF THE ANIMAL KINGDOM a. Mammalia b. Aves (birds) c. Reptilia (reptiles) d. Amphibia (frogs, newts, etc. e. Pisces (fish) f. Cyclostomata (round mouthed animals such as lampreys) g. Cephalochordata (amphioxus) h. Urochordata (sea squirts) i. Hemichordata (the balanoglossus) a. to f. have skulls, but g. to i. are small classes of skull-less animals with rudimentary spinal cords. 2. Vertebrates without Backbones a. Mollusca (snails, shellfish) b. Anthropoda (spiders, insects, crustaceans) c. Echinodermata (star fish, sea urchins) d. Annelida (worms, leeches) e. Coelenterata (jelly fish, sea anemones) f. Porifera (sponges) *Protozoa These are the first forms of life and include amoeba, infusorians and blood parasites, and are said to belong to their own kingdom with their own classification of life. The problem in deciding the limits of the Animalia kingdom is a reflection of the natural world, where boundaries are blurred and evolution leaves intermediates between major groups in its path. Origins and Relationships The multicellular animals, or Metazoa, apparently arose from animal-like, unicellular creatures, or Protozoa. There is no clear evidence of the precise relationships because the fossil record is not very good, and there has been some extinction of the intermediate forms. However, several evolutionary routes are possible. For example, there are certain animal-like flagellates (protozoans that have one or more lash-like appendages, used for locomotion) that occur as colonies and could quite easily have evolved into more elaborate organisms. In addition, the embryonic stages of some animals display a sequence of changes that provides a reasonable evolutionary model. This is a unicellular stage, followed by an undifferentiated colony stage such as a hollow ball of cells, the blastula stage. This is, in turn, followed by a gut and the gastrula stage.

NOTE: the blastula stage is when the embryo is at an early stage of development. The gastrula stage is an embryonic stage that develops from the blastula. Other theories suggest different transitional forms, such as a protozoan with many nuclei in one cell. Body Organisation The various kinds of animals have body plans that can be interpreted functionally and historically. Therefore, from these plans, the use of comparative anatomy enables scientists to classify animals into major groups and to trace and explain their evolution. Living organisms consist of cells organised into tissues which are then combined to form organs and systems. Body organisation is tailored to the specific needs of individual species for particular activities: movement respiration sensitivity growth reproduction excretion nutrition The Gut The gut is a basic body part. This must have arisen early in the evolution of the metazoans. Even the simplest of animals, the sponges, have internal cavities that function in the feeding process. However, the openings are not comparable to a mouth or an anus. Furthermore, sponges have tissues, but no real organs or nerves, and there is a lack of symmetry. The more complex jelly fish are more active animals that feed largely with their tentacles. Jelly fish have a gut, with a mouth, but they do not have an anus. They have a nervous system, but no brain or head. Also, the jelly fish does not have bilateral symmetry. In other words, it does not have a left or right side, as have the bodies of more advanced animals, including humans. Instead, jelly fish exhibit radial symmetry (symmetry around a central axis). Symmetry Symmetry provides a further basis for dividing most animals into two grades: 1. Radiata - the tissues of the radiata have only two major layers. 2. Bilateria - the tissues of the Bilateria have three layers. This is because there is an addition of a middle layer (the mesoderm) between the outer layer (ectoderm) and the inner layer (the endoderm). In the embryological development of animals, the ectoderm produces the skin and the nervous system, the endoderm the lining of the gut, and the mesoderm the remaining body structures, such as muscles. Bilateral symmetry is an evolutionary development linked with an increasing capability of active locomotion, although in later lines of evolution, locomotion has often been lost. Movement in one direction is eased by the development of a head, with a brain and sense organs at the leading end. Protostomia Within the bilateria, some phyla that differ as adults have been linked based on early embryology. Such groups are founded by how the cells divide and how the various organs are formed. For example, the basic divisions of:

i) The Protostomia, in which the embryonic mouth persists. ii) The Deuterosomia, in which the new mouth is formed. The following animals are Protostomia: Coelom The ancient bilaterian had a gut, but no other body cavity. Because of the absences of any such cavity, or coelom, the animal could be called an "acoelomate". It was also lacking an anus and a circulatory system, but it probably had a simple excretory system. Among the existing animals, this stage is probably best represented by flat worms, or to give them their scientific name (Phylum: Platyhelminthes). The lack of a circulatory system and an anus makes for an inefficient distribution of materials in the body. The nemertean worms (phylum: Rhynchocoela) have a circulatory system and an anus, but their locomotion is still slow and clumsy. The origin of the coelom was a major advance, because of the addition of the gut. This added body cavity allowed for the movement of internal organs. In some animals, this also doubles as a circulatory system and a skeleton, if its contents are under pressure. Two basic types exist: A true coelom is a cavity within the mesoderm, covered with a layer of tissue called the "epithelium". These animals are called "eucoelomates". A pseudo-coelom does not have this covering of tissue. These consist of some worm-like animals and they are called "pseudocoelomates". Such animals are generally of modest size and they possess poor locomotion. However, they are quite successful in some of their habitats. Eucoelomates can be subdivided based on how the coelom forms in embryology: The Schizocoela (also known as Schizocoelomate) form a coelom by splitting the mesoderm. The true Schizocoela are related to annelid worms (phylum: Annelida). Segmentation arose in this group. This is a serial repetition of groups of body parts. It is an arrangement thought to provide better locomotion. The Enterocoela (Enterocoelomate) form the coelom as an outgrowth of the gut. The lophophorates or Tentaculata is transitional between the Schizocoelomates and the Enterocoelomates. Members of this small group have a crown of tentacles, used for feeding; they are modified to a sedentary way of life. The arthropods (phylum: Arthropoda) retain this segmentation but they add an external skeleton. The molluscs (phylum: Mollusca) have reduced coeloms and there is very little indication of segmentation, however, they have a characteristic shell and a soft body. Deuterostomia This type comprises the enterocoels, echinoderms, arrow worms, hermichordates and chordates, the rest of the animal kingdom. These phyla are united, in the main, by development characteristics and they may be related to the lophophorates, some of which have an enterocoelous manner of forming the coelum. Also, no segmentation, of the form found in annelids, exists.

Another important link of the deuterostomes to the lophophorates is the presence, in some members of both groups, of three pairs of coelomic cavities and three corresponding body regions. The adult deuterostomes have become well modified, and arrow worms are equipped for floating and swimming. Echinoderms have lost their bilateral symmetry and they have reverted to radial symmetry, most often with five rays, for example, the starfish. The worm-like hemichordates have a very simple structure, and such advanced features as a complex brain and the capability of rapid locomotion evolved with the chordate lineage. SUMMARY OF PHYLA The following is a brief summary of the phyla, grouped into some larger assemblages as discussed previously. The number of known animal species is approximately one million. This does not include fossil species. The Parazoa Only one phylum exists in this, the most primitive division of the animal kingdom. Phylum Porifera (sponges) Sponges are simple, multicellular animals with tissues, but no distinct organs. Most of the sponges are marine (salt water) but a few do occur in fresh water. They live attached to a substrate (the surface on which an organism grows). They feed by drawing water into the body through pores, and then extracting food particles with flagellated cells. Most of the activities of the body are carried out by cells acting independently or in small groups. Sponges do not have a nervous system, but they do react to stimuli. They have a skeleton that consists of fibres, minerals, or both. There are around 4,800 species of sponges known. The Mesozoa This group consists of two phyla, the Orthonectida and the Dicyemida. They are simple parasitic worms of uncertain relationships. Mesozoa means "middle animals", and gives suggestion to the fact that they are living fossils, but they may be degenerate forms of unknown ancestors. There are around 50 species known. The Radiata These are animals with radial symmetry. They have two cell layers, the endoderm and the ectoderm. Definition: Radial symmetry (biology) The condition in which an organ or the whole of an organism can be divided into two similar halves by any one of several planes which include the centre line. Ref: Chambers Science and Technology Dictionary. Phylum Coelenterata These are true jelly fish and hydroids, coral and sea anemones. The phylum is also called Cnidaria, especially when it is extended to include the Ctenophora, described below. The stages of a coelenterate's life history include an attached polyp, as found in sea anemones, a free swimming medusa, as found in jelly fish, or both. Prey is taken with stinging capsules, generally on the tentacles. These animals are marine (salt water) - except for a few fresh water forms such as Hydra. There are three classes and around 5,300 species.

Phylum Ctenophora These are the comb jellies. These marine animals resemble true jelly fish, but they do not have a polyp stage. They swim by using bands of hair like cells resembling combs. The prey is taken by means of sticky tentacles. There are about 80 species known. THE ACOELOMATE BILATERIA The two major phyla consist of small to moderate sized worms with bilateral symmetry and they have no coelom. Phylum Platyhelminthes These are flat worms. They have no anus or circulatory system and they are structurally simple, although their hermaphroditic reproductive system is quite complex (hermaphroditic - having both male and female organs). Their flat shape is necessary because the tissues must be close to the surface to help gas and nutrient exchange with the environment. The free living class, Turbellaria, is abundant in the sea and fresh water and rare on land. Two classes are parasitic: Trematoda (flukes) Cestoda (tapeworms) There are about 13,000 species known. Phylum Nemertina (also spelt Nermertea by some scientists), or Rhynchocoela These are known as ribbon worms. They are elongate worms and possess a circulatory system and an anus. Ribbon worms are very common in the sea and rare on land. Prey is taken with a proboscis that extends through a tiny pore. There are around 800 species known. THE PSUEDOCOELOMATES The body of these animals is small to microscopic. They are worm-shaped animals that lack a circulatory system. Most psuedocoelomates are often grouped into a single phylum, with many classes. Phylum Nematoda These are roundworms. They are elongate and have a firm covering called cuticle and a body supported by fluid under pressure. These animals generally feed by sucking fluid or by taking in small particles or soft materials. They are abundant but not conspicuous. They live in soil and in marine and fresh water sediments. Some of them, as parasites, can cause serious diseases. There are about 10,000 species known. Phylum Gastrotricha These are tiny short bodied, marine and fresh water worms. They are less than one millimetre in length. There are about 170 species known. Phylum Nematomorpha This is a minor group of worms that resemble roundworms. They are parasitic in arthropods when young, they are briefly free living and aquatic as adults. There are about 230 species known.

Phylum Acanthocephala These are spiny headed worms. They are parasitic as adults, in the guts of vertebrates, and as juveniles in the tissues of various animals. These worms do not have a gut, an alimentary canal or a mouth - they have a spiny attachment organ on the head. They have a superficial resemblance to tapeworms. There are about 500 species known. Phylum Kinorhyncha These tiny short bodied marine worms have spiny bodies and a spiny proboscis. They have a length of less than one millimetre. There are about 100 species known. Phylum Rotifera (Wheel animalcules/animals) Rotifers are so named because of the wheel-shaped organ on the head. This organ is used in feeding and swimming. These animals are often microscopic. They are abundant in fresh water. There are about 1,500 species known. Phylum Priapulida These free living marine worms have spiny heads. There are about 8 species known. Phylum Entoprocta This is a moss animal. It is very small, stalked and is either a marine or fresh water animal. Entoprocts feed by means of tentacles. There about 75 species known. Phylum Lucifera This phylum was only established in 1983. It consists of marine sediment dwellers, only 0.5 millimetres long. They are free swimming larvae and sedentary adults. They have mouth cones that can be retracted into a spiny head, itself retractable. EUCOELOMATES: THE TENTACULATA These coelomate animals have a short body and a crown of tentacles called a lophophore. Phylum Phoronida Phoronoids have a U-shaped gut. This is because the lower part of the body is greatly elongated. These animals live in tubes, with the lophophore and the anus at the open end. The adults are from one to ten centimetres in length. All phoronoids are marine. There are about 18 known species. Phylum Ectoprocta or Bryozoa (moss animal) The ectoprods, polyzoans, or true bryozoans are small animals that resemble phoronoids. They live in colonies and inhabit a hardened covering, they are primarily marine. There are about 3,500 species known. Phylum Brachiopoda (lampshells) These animals have a superficial resemblance to clams. However, they have upper and lower shells rather than left and right. These animals are marine. There are about 230 species known.

EUCOELOMATES: THE TROCHOZOA The following phyla frequently possess a juvenile stage called a trochophore larva. They may be derived from an annelid type ancestor, judging by their widespread segmentation and the frequent occurrence of paired nerve cords that are ventral to the gut. Phylum Annelida Annelids possess a well-developed coelom, a soft body and well-developed segmentation. They have bristle like structures, called "setae", these are used in crawling. This group includes earthworms (class Oligochaeta), leeches (class Hirudinea) and the less familiar bristle worms (class Polychaeta). There are some animals of uncertain position, which are sometimes treated as classes of annelids, sometimes placed in separate phyla. Echiura and Pogonophora (beard worms), two minor groups within the polychaetes, Archiannelida and Myzostomida are often considered to be independent classes. There are about 8,700 species known. Phylum Sipuncula These are peanut worms. They are moderate sized marine worms, having a sac-like body with a long proboscis. Their length is approximately 3 centimetres. These animals may be simplified annelids. There are about 250 species known. Phylum Mollusca This is the second largest animal phylum, and includes snails and clams. Molluscs have a typical hard shell and a soft body. There are still a few traces of segmentism (metamerism), and the coelom is small, the main body cavity is part of the circulatory system. Some forms, for example octopuses and squid attain a considerable size. The seven mollusc classes are: Aplacophora Polyplacophora Monoplacophora Gastropoda (snails and slugs) Bivalvia (clams and allies) Cephalopoda (octopuses, squids & allies) Scaphopoda (tusk shells) There are at least 50,000 species known. Phylum Arthropoda This is the largest animal phylum, and this is partly due to the fact that so many insects exist. The body of an arthropod is covered with a hard jointed skeleton. Arthropods are very much in abundance and they are successful in almost all habitats. The body still remains segmented and the coelom has been reduced. There are three small transitional groups that are sometimes included in the Arthropoda, and these are sometimes listed as independent phyla. These are: Onychopora Tardigrada Pentastomida The classes of higher arthropods can be grouped into assemblages: Those with jaws (mandibulates). These include the Crustacea, for example lobsters and crabs. The allied Myriapoda (many legs), which includes centipedes and millipedes. Insecta (insects) Arthropods that have mouthparts called "chelicerae" include the Pycnogonida (sea spiders), Merostomata (horseshoe crabs) and Arachnida (spiders). There are at least 838,000 species.

EUCOELOMATES: THE DEUTEROSTOMIA This large group includes all the remaining animals. The name of the group suggests that the mouth is produced secondarily, as a new formation, in the embryological development. Phylum Chaetognatha These are arrow worms; they are small, active and exclusively marine swimmers of uncertain relationship. There are about 50 known species. Phylum Echinodermata Echinoderms derive their name from their spiny skins. They are slow moving and rely mainly on small processes called "tube feet" for locomotion. The group includes starfish and sea cucumbers. All the species are marine. The five existing classes are: Crinoidea (feather stars) Asteroidea (sea stars) Ophiuroidea (brittle stars) Echinoidea (sea urchins) Holothuroidea (sea cucumbers). There are about 6,000 species known. Phylum Hemichordata These are acorn worms, simple worm-like marine animals. They have a few characteristics that link then to the chordates. Among these are traces of what may be a notochord in addition to a system of gill slits. However, the larval body of the worm increases, which seems to indicate a link to the echinoderms. There are about 230 known species. Phylum Chordata Chordates include animals with backbones (vertebrates) and some related invertebrates. At some time in their life, chordates all possess a stiff rod, called a "notochord". This lies above the gut. In vertebrates, a series of bones (vertebrae) replace the notochord. Two sub-phyla of invertebrate chordates exist: The Tunicata (sea squirts). These become highly modified as adults and attach to a substrate. They feed with gill slits. Only the free swimming larvae retain a notochord. They are marine. Approximately 1,300 species are still in existence. The Cephalochordata (lancelets). These resemble very simple fish. They live in the sea and extract food from the water with their gill slits. Approximately 25 species exist. The remaining Chordata belong to the sub-class Vertebrata, and have a backbone. Of the approximately 42,000 species known, half of them are fish. Therefore, although the group is successful, it is outnumbered by arthropods and molluscs.

Seven classes of this phylum are generally recognised: Agnatha (jawless fish such as lampreys) Chondrichthyes (cartilaginous fish such as sharks and rays) Osteichthyes (bony fish) Amphibia. This class contains such semi-aquatic forms such as salamanders, toads and frogs. Reptilia (reptiles). This class is better adapted to life on the land and it includes turtles, snakes, lizards and crocodilians. Aves (birds). This class is noteworthy not only for flight, but for warm blood and an insulating layer of feathers. Mammalia (mammals). This class is characterised by the possession of hair and mammary glands that secrete milk. This group is also warm blooded. It includes humans. White Rhinoceros (Ceratotherium simum) PARASITES Parasites have been mentioned in previous sections of this lesson. They can be defined as: Any organism that lives on or in another living organism, and derives part or all of its nutrients from the host without contributing anything beneficial to the host. In most cases, parasites damage or cause disease to the host. Such parasites as lice that live on the surface of the host are known as "ectoparasites". Those that live within the body of the host, for example, threadworms, are known as "endoparasites".

The scientific study of parasites is known as "parasitology". There are permanent parasites that pass most of their lifecycle in or on their host, and there are temporary parasites that only spend a brief period of time in or on the host, and are free living organisms for the remainder of their life cycle. Some parasites cannot survive without a host; these are called "obligate parasites". Parasites that can feed either on a host or on dead material are called "facultative parasites". Some require different organisms for various stages of their life cycle. An example of this type of parasite is the heteroecious parasite of which the liver fluke is a species. Autoecious parasites, such as pinworm, pass the parasitic stage of their life cycle in only one host. Human Parasites Parasites that have humans for hosts include: Viruses Rickettsias - this is a parasitic microorganism that causes typhus and other febrile diseases. Fungi Protozoans Worms Flukes Bacteria Viruses and rickettsias are not usually considered to living organisms, but they have methods of transmission that are identical with other parasites and receive nourishment from the host. In humans, viruses and bacteria are the cause of most of the infectious diseases. Protozoans also cause disease, for example, the lethal sleeping sickness is caused by a one-celled organism called "Trypanosoma". Parasitic Plants Parasitic plants feed on other plants. Among which we may have: Partial Parasites These parasites derive some of their nutrients from the host. Partial parasites have green leaves and they are capable of synthesising carbohydrates, proteins and fats by the process of photosynthesis. However, they derive all their water, nitrogen and mineral salts from the host plant. A common example of a total plant parasite is the mistletoe. Mistletoe is typical of a group of plants that never form their own roots. The seeds of these plants are carried from tree to tree by birds. They develop penetrating outgrowths, known as "Haustoria". These outgrowths pierce the host and enter the plants conducting tissue. Total Parasites Total parasites have vestigial leaves that do not possess chlorophyll and they do not have any functioning roots. Dodder, a climbing parasitic plant with slender, leafless, threadlike stems, is of the genus Cuscula. It has a small seed that germinates in the ground, thus forming a small root that attaches the plant to the soil, but derives no food from it. A long thin pliable stem grows above the ground, until it contacts a green plant which it then climbs. The ultimate in parasitic plants is exhibited in certain tropical plants of the family Rafflesiaceae. These plants have neither stems nor leaves, and they grow only on specified parts of green plants. The germinated seeds send Haustoria directly into the host. The only other organs of these parasites are non-petalled flowers. These flowers are composed of huge, fleshy petal-like structures that give off an odour of decaying meat. Insects are attracted by this distinct odour, and they carry the pollen from flower to flower.

ENDANGERED SPECIES Endangered species are those flora and fauna species that are in immediate danger of extinction. Many countries classify endangered species according to the degree of endangerment they face. The International Union for the Conservation of Nature and Natural Resources (IUCN) has been assessing the status of plant and animal species on a global scale for over 40 years. They have created 9 categories to determine the relative risk of extinction or record of extinction based on set critieria. The IUCN Red List Categories are: Extinct (EX) no reasonable doubt that the last individual has died. Extinct in the Wild (EW) known only to survive in cultivation. Critically Endangered (CR)* - considered to be facing extremely high risk of extinction in the wild. Endangered (EN)* - considered to be facing a very high risk of extinction in the wild. Vulnerable (VU)* - considered to be facing a high risk of extinction in the wild. Near Threatened (NT) likely to qualify for a threatened category in the near future. Least Concern (LC) widespread and abundant taxa. Data Deficient (DD) inadequate information to make a direct assessment of the species status. Not Evaluated (NE) not yet evaluated against criteria. *threatened categories Some examples of species listed globally as threatened include: Critically endangered species, such as the Californian Condor. These species possibly cannot survive without human intervention. Threatened species, such as the grizzly bear. These threatened species are abundant in parts of their range, but they are declining in total numbers. Rare species. These exist in relatively low numbers over most of their range, but they are not necessarily in immediate danger of extinction. North American brown bear (Ursus arctos horribilis) Extinction is a normal process in the course of evolution. Throughout geological time many more species have become extinct than those species that exist today. These species slowly disappeared because of climatic change, natural disasters, and their inability to adapt to changes, such as temperature, competition and predation.

Since the beginning of the seventeenth century, the process of extinction has accelerated with great rapidity. This has been caused by the impact of human population growth and the effect of technological advances on natural ecosystems. The majority of the environments in the world are changing faster than the ability of most species to adapt to these changes through the process of natural selection. The Causes of Endangerment or Extinction Species become extinct for a number of reasons. The primary factor leading to the risk of extinction is the destruction of habitats. This the primary cause and is affected by the following: The drainage of wetlands The conversion of shrub lands to grazing lands The cutting and clearing of forests. This is especially true in the tropics, where o the rainforests will be completely eliminated by the year 2010 if destruction o continues at the present rate. Urbanisation and suburbanisation Highway construction. The construction of dams. As the remaining habitats become fragmented into 'islands' the animal populations crowd into these smaller spaces, thus causing further destruction of habitats; the species in these small "islands' lose contact with other populations of their own species. This reduces the genetic variation, and makes them less adaptable to environmental change. These small populations are highly vulnerable to extinction (e.g. from natural disasters such as fires), and for some species, the fragmented habitats become too small to support a viable population. Since the beginning of the seventeenth century, the commercial exploitation of animals for food and other products has been the cause of many species becoming extinct or endangered. For example, the slaughter of the great whales for oil and meat brought them to the very edge of extinction, before international treaties restricted the harvesting of these animals. The African rhinoceroses that are killed for their horns have also become critically endangered. In the nineteenth century the great auk and the American passenger pigeon became extinct because of over hunting, while the California parakeet became extinct because of a combination of habitat destruction and over hunting. The introduction of diseases, parasites and predators, against which the indigenous flora and fauna have no defence, has also exterminated or greatly reduced some species. For example, blight was accidentally introduced to the North American hardwood forests with the result of the complete elimination of chestnut trees. In Australia, the introduction of species such as cats and foxes has resulted in the extinction of at least forty species, probably the greatest rate of modern extinctions seen in any country, as well as the decline of many other species. Predator and pest control can also have adverse effects on the ecosystems, for example in America, excessive control of prairie dogs has led to the near elimination of one of their natural predators, the black footed ferret, while in Australia the introduction of the cane toad to control pests in sugar cane crops, has seen that animal become a major pest in its own right, threatening many native species. A further problem is the introduction of exotic plants. They often thrive in their new homes, particularly when they are no longer exposed to diseases or predators or climatic controls that may have kept them in check in their original habitats. In Australia, for example, many introduced species have become environmental weeds displacing indigenous vegetation, while in places such as South America and the United States of America; Australian plants have become major environmental weeds there.

Another important cause of extinctions is pollution. Toxic chemicals and especially chlorinated hydrocarbons such as dichloro-diphenyl-trichloroethane (DDT) and the polychlorinated biphenyls (PCB's) have become concentrated in food chains. This affects mainly those animals which are at the end of the food chain, where the accumulation of such chemicals reaches its highest concentration. Both DDT and PCB's interfere with the calcium metabolism of birds. This causes soft-shelled eggs and malformed chicks. PCB's also impair reproduction in some carnivorous animals. Water pollution and increased water temperatures have wiped out endemic races of fish in several habitats. Pollution will be dealt with in greater detail in a later lesson of this course. Efforts for Preservation Some governmental and private efforts have been mobilised to save the declining species. The immediate approach is to protect a species by legislation. In many countries laws have been enacted to protect wildlife from commercial trade and over hunting. International efforts centre on the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This was ratified by fifty-one nations in 1973. Other nations have since joined. The purpose of the convention is to restrict the exploitation of wildlife and plants by regulating and restricting trade in endangered species. However, the effectiveness of such laws in various countries depends on enforcement and support by the people and the courts. As a result of the lack of law enforcement, the willingness of some segments of society to trade in endangered species, the high prices obtained for products from such wildlife and plants, and the activities of poachers and dealers who supply the trade, the future of many species is in doubt, in spite of their so called legal protection. It would appear that the penalties for conviction on these matters are too low. It should be realised that by their actions, these people are putting the inhabitants of earth and indeed the earth itself, in jeopardy by their actions, therefore the penalties should be increased to such an extent as to make the law breakers have second thoughts. Efforts to save endangered species also include the propagation of breeding stock for release in the wide. This is known as captive breeding programs, and is to either restore a breeding population or to augment a natural population. Another approach involves the determination of critical habitats that must be preserved for endangered species. These habitats may be protected by the establishment of reserves. However, the value of these reserves may be limited because of the "island' effect. It is also usual for the objections of special interest groups to make land preservation for the protection of endangered species a difficult matter. Some international treaties and/or conventions have been established which aim to preserve critical habitats. Examples include the RAMSAR agreement which is aimed at preserving wetlands and in Australia the Chinese-Australia Migratory Bird Agreement (CAMBA) and the Japanese- Australia Migratory Bird Agreement (JAMBA).

CASE STUDY: THREATENED ANIMALS SPECIES IN QUEENSLAND, AUSTRALIA Although there are many animals throughout Australia that do not live in Queensland, this list is provided here to give students an idea as to the extent just one state in one country may list threatened animals. Students are asked to compile their own lists for their state or country to get a more localised idea of their district. Birds Presumed Extinct Paradise parrot (1922) Endangered Eastern bristlebird, red goshawk*, southern cassowary (southern population)*, regent honeyeater, golden-shouldered parrot*, night parrot*, doubled-eyed fig parrot (Coxen's)*, gouldian finch*, star finch, herald petrel Vulnerable Rufous scrub-bird, beach thick-knee, southern cassowary (northern population)*, squatter pigeon, yellow chat, grey falcon, little tern, purple-crowned fairy-wren, southern emu-wren, plains wanderer, red-tailed tropicbird, black-throated finch, crimson finch, marbled frogmouth, pink cockatoo (Major Mitchell), glossy-black cockatoo, double-eyed fig-parrot (Macleay's), eclectus parrot, ground parrot, powerful owl, rufous owl, black-breasted button-quail*, masked owl (northern species) Mammals Presumed extinct Western quoll (unknown), downs hopping-mouse (1840), white-footed rabbit-rat (1875), desert rat-kangaroo (1935), dusky fruit-bat (1854) Endangered Julia creek dunnart*, Taphozus troughtoni, bridled nailtail wallaby, bramble cay melomys, dusky hopping-mouse, plains rat, carpentarian rock-rat, mahogany glider*, northern bettong*, greater bilby*, northern hairy-nosed wombat*. Vulnerable Humpback whale*, dugong*, hairy-footed dunnart, lesser-footed dunnart, mulgara, kowari*, spotted-tailed quoll, common sheathtail-bat, orange horseshoe-bat, fawn horseshoe-bat, greater wart-nosed horseshoe-bat, lesser wart-nosed horseshoe-bat, torresian flying fox, flute-nosed bat, brush-tailed rock-wallaby, proserpine rock-wallaby*, northern hoppingmouse, hastings river mouse*, yellow-bellied glider (northern subspecies)*, Pteropus macrotis epularis Fish Endangered Elizabeth springs goby*, edgbaston goby*, red-finned blue-eye* Vulnerable Oxleyan pygmy perch*, honey blue-eye*

Frogs Endangered Litoria lorica*, torrent tree frog*, Lynyakalensis*, L. rheocala*, Nyctimystes dayi*, Mixophyes fleayi*, giant barred frog*, southern gastric brooding frog*, northern gastric brooding frog*, sharp-snouted torrent frog*, Mount Glorious torrent frog*, Eungella torrent frog*, Taudactylus rheophilus* Vulnerable Freycinet's frog, Litoria oblongburensis, Taudactylus pleione, Crinia tinnula Butterflies Endangered Apollo jewel butterfly, Diane moonbeam butterfly, Illidge's ant-blue butterfly*, piceatus jewel butterfly, Nacaduba pactolus cela, Australia fritillary butterfly, nigger Vulnerable Purple brown-eye butterfly, Acropodipsas hirtipes, A. melania, Danis danis syrius, apollo jewel butterfly (Hypochrysops apollo phoebus), H. theon, Jalmens evagorus eubulus, satin blue butterfly, Australia hedge blue butterfly, Australian beak butterfly, Richmond birdwing butterfly Reptiles Endangered Loggerhead turtle*, olive ridley turtle*, leatherback turtle*, Lerista allanae* Vulnerable Mary River tortoise*, Fitzroy River tortoise*, green turtle*, hawksbill turtle*, flatback turtle*, saltwater crocodile*, Dunmall's snake*, ornamental snake*, Delma labialis*, Paradelma orientalis*, D. torquata*, Anomalopus mackayi*, yakka skink*, Lerista vittata* *These threatened species are subject to continuing research. Conservation plans and management programs apply to many. SELF ASSESSMENT Perform the self-assessment test titled Test 3.1 If you answer incorrectly, review the notes and try the test again. SET TASK Contact the government authority in your area (e.g. Conservation Dept.) and find out which plants and animals in your region or state are endangered or threatened. What is being done to protect them? ASSIGNMENT Download and do the assignment called Lesson 3 Assignment.